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fn int_digits(input: &str) -> Vec<u16> {
input
.chars()
.map(|d| d.to_digit(10).unwrap() as u16)
.collect()
}
pub fn gs1_checksum(input: &str) -> u8 {
let digits = int_digits(input);
let mut even: u16 = 0;
let mut odd: u16 = 0;
for i in 1..=digits.len() {
let curr = digits[digits.len() - i];
if i % 2 == 0 {
even += curr;
} else {
odd += curr;
}
}
let mut check = (3 * odd + even) % 10;
if check > 0 {
check = 10 - check;
}
check as u8
}
#[test]
fn test_gs1_checksum() {
assert_eq!(0, gs1_checksum(&"0360843951968".to_string()));
assert_eq!(8, gs1_checksum(&"8061414112345".to_string()));
}